Stabilized polyolefins



United States Patent ABSTRACT OF THE DISCLGSURE A polyolefin composition stable to metal induced thermal decomposition containing, in addition to known stabilizers, an organic phosphorous compound prepared by condensing 3 moles of 4,4'-thio-bis(6-t-butyl-m-cresol) with 1 mole of P61 or P001 This application is a c-ontinuation-in-part of our copending US. application Ser. No. 538,544, filed Mar. 30, 1966, which in turn was a continuation of Ser. No. 133,038, filed Aug. 22, 1961, entitled Stabilized Polyolefins, both of which are now abandoned.

The present invention relates to stabilized polyolefins.

It is known that high-polymer substances are sensitive to the action of oxygen, heat and light and under such action undergo a decomposition which is evidenced by embrittlement. This is especially true of polymers of the olefin series. Polymers of ethylene prepared by the high pressure polymerization process as well as polymers of ethylene prepared by the low pressure polymerization process and polymers of a-olefins, for example, of propylene, butene and 4-methylpentene-1, which have been prepared by the low pressure polymerization process must therefore be protected against the action of heat, oxygen and light by the addititon of substances having a stabilizing effect.

For the stabilization of polyolefins there are used, for example, substituted phenols such as 2,6-di-t-butyl-pcresol, or sulfur-containing phenolic compounds such as 4,4'-thio-bis-(G-t-butyI-rn-cresol). Amines such as, for example, dinaphthyl-p-phenylene-diamine are also known as stabilizers. Compositions comprising a phenolic compound and an organic sulphidic compound produce especially good synergistic stabilization effects, in particular on polymers containing tertiary carbon atoms in the chain. In Belgian Patent 577,252 is described the use of the condensation product of nonyl phenol and acetone in combination with thio-dipropionic ,acid lauryl ester which enables the the-rmostability of polyolefins, in particular of polypropylene, to be considerably improved.

It is also known that the presence of certain metals, for example, copper and its alloys, manganese, cobalt and iron, considerably impairs the thermostability and the resistance to oxidation of polyolefins. Shaped articles of polyolefins, for example, which contain parts of the above-mentioned metals, have much worse aging properties. Polyolefins can therefore be used only to a limited extent as insulating material for the coating of electric conductors since at elevated temperatures an insulation CH3 CH l l P Ho p o efins h his. n c nt t w th. h wma tioned metals becomes brittle relatively quickly if it does not contain an appropriate stabilizer. Protective coatings which have been applied to metals by sintering in a fluidized bed become likewise brittle after a short time for the reason given above.

Now we have found that the thermostability of polyolefins, especially that of polyolefins containing tertiary carbon atoms in the polymer chain such, for example, as polypropylene, polybutene and poly-4-methylpentene-1, can be considerably improved, preferably in cases in which the said polyolefins are in contact with metals having a catalytic effect on the decomposition, for example, copper, manganese or the alloys thereof, by adding to the polyolefins containing known stabilizers as a co-stabilizer 0.1 to 2%, preferably 0.2 to 1%, of an organic phosphorus compound prepared by the reaction of PCl or O=PCl with 4,4'-thio-bis-(6-t-butyl-m-cresol). Serviceable stabilizers are obtained when the two compounds are reacted in molar proportions within the range of 6:1 to 3:2. Preferably, the stoichiometric molar proportion is 3: 1.

The reaction products are predominantly compounds having approximately the following general formula when the molar proportion of reactants is about 3:1.

CH CH CH CH3 3 4,4-dioxy-diphenyl-dimethyl-methane,

bis- (4-oxy-3-methyl-phenyl -propane- 2.2) 4,4'-dioxydiphenyl,

bis- 4-oxy-3 ,5 -dimethyl-phenyl) -methane,

bis- 4-oxy-3 ,5 -di-t-butyl-phenyl) -methane,

bis- 2'oxy-3-t-butyl-5-methyl-phenyl) -methane, bis- 2-oxy-5-chlorophenyl) -methane,

bis (4-oxy-3-methyl-phenyl -pentane,

bis- 2-oxy-phenyl -cyclohexane, 4,4'-thiobis-(6-t-butyl-m-cresol) Naphthols and bisnaphthols, for example, fi-dinaphthol, bis-(2-oxy-naphthyl)-methane, bis-(2-oxy-3--nonylnaphthyD-methane; terpene-substituted phenols and hisphenols, for example, 6-isobornyl-o-cresol, 6-isobornyl- 1,2,4-xylenol, 2,6-di-isobornyl-p-cresol, '6-is-obornyl-3,4- dimethyl-phenol, 2,6-di-isobornyl 3,4 dimethyl phenol, 6,6 methylene bis (2-isobornyl-4-methylphenol), 6,6- methylene-bis- 2,4-di-isobornyl-phenol).

The stabilizing effect obtained is particularly good when the co-stabilizers according to the invention are used in admixture with a composition containing up to about 0.5% of phenolic stabilizers and up to about 0.5 of organic sulphidic compounds. Particularly suitable compounds are: thioet-hers, preferably those of J aliphatic alcohols containing 4 to 18 carbon atoms such, for example, as di-octyl-sulphide, di-dodecyl-sulphide, dioctadecyl-sulphide and bis(2-oxy-napht-hyl)-su1phide and the corresponding polythioethers, for example, di-dodecadded alone or in admixture with the other stabilizers, the substances being added in the pulverulent form to the pulverulent polymers in a high speed mixer or dissolved in an appropriate organic solvent and the resulting yl-disulphide, di-octyl-trisulphide, di-octadecyl-tetrasul- 5 solution beingadded to the polymer. It is often suitable phide, bis-(Z-oxy-naphthyl)-disulphide; thioand polyfirst to mix the stabilizer with a small quantity of the thio-carboxylic acid alkyl esters, preferably those of alipulverulent polymer so that a polymer master batch is phatic alcohols containing 4 to 18 carbon atoms such, formed which contains 30 to 40% of stabilizer and which for example, as thio-di-acetic acid dodecyl ester, thio-dienables the desired concentration of stabilizer to be impropionic acid lauryl ester, di-thio-di-butyric acid, octa- 1O parted to the total quantity of the polymer. decyl ester, di-thio-divaleric acid butyl ester, trithiodidec- The stabilized powders were Worked up on a heated ane-carboxylic acid nonyl ester, tetrathio-dibutyric acid press into foils 1 mm. thick under the following condioctyl ester and s-t-butyl-mercapto-acetic acid lauryl ester. tions:

It is particularly preferred to use the co-stabilizers Preheating for minutes at 200 C. under contact according to the present invention in admixture with up pressure; pressing for 2 minutes at 200 C. under a presto about 0.5% of the condensation product obtained from sure of 10 kg./cm. cooling within 7 minutes under a 2 mols of nonyl phenol and 1 mol of acetone (according pressure of 50 kg./cm.

to US. 3,020,259), or in admixture with the said con- The following examples serve to illustrate the invention densation product and up to about 0.5% of thiodipropibut they are not intended to limit it thereto, the parts heonic acid lauryl ester. ing by weight and the percentages being likewise by weight The low pressure polyolefins which are to be stabilized and calculated on the quantity of polymer used. with the stabilizers according to the invention may be E l 1 d 2 greparetsi gccozrdrng to the process described 111 Belgian The reaction product of atent 3 ,78 Detailed statements concerning the prepcresol) and P013 was pmpared by reacting the two Manon of pqlyolefiris by the low Pressure polymenzanon stances in a molar ratio of 3:1. The cresol derivative was g i g cannter ahaflbe fomid f 72 to of the dissolved at 110 C. in hot toluene and at this temperay Ra and Alhson entltled Polyethylene (In/Ear ture PCl was added dropwise while stirring. A vehement scl errtllce Pujbil shers, 195g). evolution of H01 set in. After the total quantity of PC1 larl eS stcablizirs ztifcort tot the lIflVgDtlOIl art; p l h d been added the whole was boiled for about two hours y m a e or e S a 112a 0 cope under reflux. The solvent was distilled off and a light mers olefins Preferably polypropylene may resin remained as residue which, after cooling, was pulcontam monomer unitis1 oter than olefirgs, and which are verized used for coating met s, or exarnp e, i y sintering in a fluidized or for insulating Wires. The following values were obtained by analysis.

The embrittlement of plastic materials is ascertained 5 by the so-called brittle test. In this test a strip of a toil Fmmd (percent) i gs about 1 mm. thick is stored in a warming cabinet and p its flexibility is daily determined by bending it by hand Content ok at an angle of 180. In the hand bending test the em- 01 0.2 0 brittlement of the plastic material is noticeable by rup- 4O g-i 2 -2 ture. Another way of examining in particular the be- I havior with respect to embrittlement of plastic materials used as insulating material of electrical conductors is the sukfstanlfmuy the same analysls was found when So caued curl testy According to this method an e160 action t1me was increased up to about 8 hours. Servicetrical conductor which is coated with plastic material is able costablhzers were'also Obtamed W9 Wound up in narrow turns around its Own vaxis and the pounds were reacted in molar proportions within the thus obtained is Stored in a warming cabinet. By range of 6.1 to 3.2. Preferably, the stoichiometrrcal the winding the plastic material is exposed to tensions. molar proporilon was i The brittleness can be noticed y cracks forming in the The following table illustrates the efiieiency of the stabilizer system according to the invention, the efficiency lflsula'flon' In Order to examme the efliclency of Stabl' being determined by the brittle test and the behavior with hzers the Presence of metals for 31111716, Copper fine respect to embrittlement of a cable, stored in a warming metal POWder was added to the polyolefin, for example, cabinet. For the purpose of comparison, the efiiciency P yp py and the embrittlemfint Was determined y 01. known stabilizers is indicated. The insulation of the the hand bending test. cables used had a thickness of 0.6 mm. The copper con- The co-stabilizers according to the invention may be ductor had diameter of 0.8 mm.

TABLE 1 [Brittle Times Measured. With Pressed Foils and Cables Made of Polypropylene] Brittle Time in Days at Curl Test (days to cracking) Concentration Ex. No. Stabilizer (chemical name) in Percent by Addition of 0.5% by Weight weight of copper powder A- 4,4-thio-bis-(G-t-bntyl-m-cresol) 0.5 104 19 4 1 22 8 B Condensation product of nonyl phenol and 0. 5 31 4 2 1 7 2 C O iiil ii sition product of nonyl phenol and 0. 5+0. 5 108 34 6 1 55 3 acetone+thiodipropionic acid lauryl ester. 1 Condensation product of nonyl phenol and 0. 5+0. 5 115 23 17 2 acetone+reaction product of 4.4-thio-bis- (G-t-butyl-m-cresol) with P013. 2 Condensation product of nonyl phenol and 0. 5+0. 6+0. 5 60 130 7 168 35 acetone+thio-di-proplonic acid lauryl ester+reaction product of 4,4-thio-bis-(6- t-butyl-m-cresol) with PCla.

and 1 mole of acetone; and up to about 0.5 of dilauryl thiodipropionate.

References Cited UNITED STATES PATENTS 6/1958 Hechenbleikner 26041 3/1964 Warren 260-4595 X DONALD E. CZAJA, Primary Examiner.

10 L. J. BERCOVITZ, Examiner.

M. J. WELSH, Assistant Examiner. 

